269 research outputs found
Obscured Starburst Activity in High Redshift Clusters and Groups
Using Spitzer-MIPS 24um imaging and Keck spectroscopy we examine the nature
of the obscured star forming population in three clusters and three groups at
z~0.9. These six systems are components of the Cl1604 supercluster, the largest
structure imaged by Spitzer at redshifts near unity. We find that the average
density of 24um-detected galaxies within the Cl1604 clusters is nearly twice
that of the surrounding field and that this overdensity scales with the
cluster's dynamical state. The 24um-bright members often appear optically
unremarkable and exhibit only moderate [OII] line emission due to severe
obscuration. Their spatial distribution suggests they are an infalling
population, but an examination of their spectral properties, morphologies and
optical colors indicate they are not simply analogs of the field population
that have yet to be quenched. Using stacked composite spectra, we find the
24um-detected cluster and group galaxies exhibit elevated levels of Balmer
absorption compared to galaxies undergoing normal, continuous star formation. A
similar excess is not observed in field galaxies with equivalent infrared
luminosities, indicating a greater fraction of the detected cluster and group
members have experienced a burst of star formation in the recent past compared
to their counterparts in the field. Our results suggest that gas-rich galaxies
at high redshift experience a temporary increase in their star formation
activity as they assemble into denser environments. Using HST-ACS imaging we
find that disturbed morphologies are common among the 24um-detected cluster and
group members and become more prevalent in regions of higher galaxy density. We
conclude that mergers are the dominant triggering mechanism responsible for the
enhanced star formation found in the Cl1604 groups, while a mix of harassment
and mergers are likely driving the activity of the cluster galaxies.Comment: 18 pages, 19 figures, submitted to Ap
Properties of Galaxies Hosting X-ray Selected Active Galactic Nuclei in the Cl1604 Supercluster at z=0.9
To investigate the role of feedback from Active Galactic Nuclei (AGN) in
driving the evolution of their host galaxies, we have carried out a study of
the environments and optical properties of galaxies harboring X-ray luminous
AGN in the Cl1604 supercluster at z~0.9. Making use of Chandra, HST/ACS and
Keck/DEIMOS observations, we examine the integrated colors, morphologies and
spectral properties of nine moderate-luminosity (L_x ~ 10^43 erg s^-1) type 2
Seyferts detected in the Cl1604 complex. We find that the AGN are predominantly
hosted by luminous spheroids and/or bulge dominated galaxies which have colors
that place them in the valley between the blue cloud and red sequence in
color-magnitude space, consistent with predictions that AGN hosts should
constitute a transition population. Half of the hosts have bluer overall colors
as a result of blue resolved cores in otherwise red spheroids and a majority
show signs of recent or pending interactions. We also find a substantial number
exhibit strong Balmer absorption features indicative of post-starburst
galaxies, despite the fact that we detect narrow [OII] emission lines in all of
the host spectra. If the [OII] lines are due in part to AGN emission, as we
suspect, then this result implies that a significant fraction of these galaxies
(44%) have experienced an enhanced level of star formation within the last ~1
Gyr which was rapidly suppressed. Overall we find that the properties of the
nine host galaxies are generally consistent with a scenario in which recent
interactions have triggered both increased levels of nuclear activity and an
enhancement of centrally concentrated star formation, followed by a rapid
truncation of the latter, possibly as a result of feedback from the AGN itself.
[Abridged]Comment: 15 pages, 9 Figures, submitted to Ap
Identifying Stars of Mass >150 Msun from Their Eclipse by a Binary Companion
We examine the possibility that very massive stars greatly exceeding the
commonly adopted stellar mass limit of 150 Msun may be present in young star
clusters in the local universe. We identify ten candidate clusters, some of
which may host stars with masses up to 600 Msun formed via runaway collisions.
We estimate the probabilities of these very massive stars being in eclipsing
binaries to be >30%. Although most of these systems cannot be resolved at
present, their transits can be detected at distances of 3 Mpc even under the
contamination of the background cluster light, due to the large associated
luminosities ~10^7 Lsun and mean transit depths of ~10^6 Lsun. Discovery of
very massive eclipsing binaries would flag possible progenitors of
pair-instability supernovae and intermediate-mass black holes.Comment: 5 pages, 1 figure, 1 table. Submitted to MNRA
A DNA Methylation Signature of Addiction in T Cells and Its Reversal With DHEA Intervention
Previous studies in animal models of cocaine craving have delineated broad changes in DNA methylation profiles in the nucleus accumbens. A crucial factor for progress in behavioral and mental health epigenetics is the discovery of epigenetic markers in peripheral tissues. Several studies in primates and humans have associated differences in behavioral phenotypes with changes in DNA methylation in T cells and brain. Herein, we present a pilot study (n = 27) showing that the T cell DNA methylation profile differentiates persons with a substance use disorder from controls. Intervention with dehydroepiandrosterone (DHEA), previously shown to have a long-term therapeutic effect on human addicts herein resulted in reversal of DNA methylation changes in genes related to pathways associated with the addictive state
Multidrug-Resistant Salmonella enterica Serovar Infantis, Israel
To determine whether rapid emergence of Salmonella enterica serovar Infantis in Israel resulted from an increase in different biotypes or spread of 1 clone, we characterized 87 serovar Infantis isolates on the genotypic and phenotypic levels. The emerging strain comprised 1 genetic clone with a distinct pulsed-field gel electrophoresis profile and a common antimicrobial drug resistance pattern
Pair-Instability Supernovae at the Epoch of Reionization
Pristine stars with masses between ~140 and 260 M_sun are theoretically
predicted to die as pair-instability supernovae. These very massive progenitors
could come from Pop III stars in the early universe. We model the light curves
and spectra of pair-instability supernovae over a range of masses and envelope
structures. At redshifts of reionization z >= 6, we calculate the rates and
detectability of pair-instability and core collapse supernovae, and show that
with the James Webb Space Telescope, it is possible to determine the
contribution of Pop III and Pop II stars toward reionization by constraining
the stellar initial mass function at that epoch using these supernovae. We also
find the rates of Type Ia supernovae, and show that they are not rare during
reionization, and can be used to probe the mass function at 4-8 M_sun. If the
budget of ionizing photons was dominated by contributions from top-heavy Pop
III stars, we predict that the bright end of the galaxy luminosity function
will be contaminated by pair-instability supernovae.Comment: 12 pages, 11 figures. Matches MNRAS accepted versio
Shyness discriminates between children with 22q11.2 deletion syndrome and Williams syndrome and predicts emergence of psychosis in 22q11.2 deletion syndrome
BACKGROUND: 22q11.2 deletion syndrome (22q11.2DS) is a common neurogenetic syndrome associated with high rates of psychosis. The aims of the present study were to identify the unique temperament traits that characterize children with 22q11.2DS compared to children with Williams syndrome (WS) and typically developing (TD) controls, and to examine temperamental predictors of the emergence of psychosis in 22q11.2DS. METHODS: The temperament of 55 children with 22q11.2DS, 36 with WS, and 280 TD children was assessed using the Emotionality, Activity, Sociability (EAS) Temperament Survey, Parental Ratings. The presence of a psychotic disorder was evaluated in 49 children and adolescents with 22q11.2DS at baseline and again 5.43 ± 2.23 years after baseline temperament assessment. RESULTS: Children with 22q11.2DS scored higher on Shyness compared to WS and TD controls. Children with 22q11.2DS and WS scored higher on Emotionality and lower on Activity compared to TD controls. Shyness was more severe in older compared to younger children with 22q11.2DS. Baseline Shyness scores significantly predicted the later emergence of a psychotic disorder at follow-up, in children with 22q11.2DS. CONCLUSIONS: Our results suggest that shyness is an early marker associated with the later emergence of psychosis in 22q11.2DS
The use of a vortex insertion technique to simulate the extratropical transition of Hurricane Michael (2000)
On 19 October 2000, Hurricane Michael merged with an approaching baroclinic trough over the western North Atlantic Ocean south of Nova Scotia. As the hurricane moved over cooler sea surface temperatures (SSTs; less than 25°C), it intensified to category-2 intensity on the Saffir–Simpson hurricane scale [maximum sustained wind speeds of 44 m s−1 (85 kt)] while tapping energy from the baroclinic environment. The large “hybrid” storm made landfall on the south coast of Newfoundland with maximum sustained winds of 39 m s−1 (75 kt) causing moderate damage to coastal communities east of landfall. Hurricane Michael presented significant challenges to weather forecasters. The fundamental issue was determining which of two cyclones (a newly formed baroclinic low south of Nova Scotia or the hurricane) would become the dominant circulation center during the early stages of the extratropical transition (ET) process. Second, it was difficult to predict the intensity of the storm at landfall owing to competing factors: 1) decreasing SSTs conducive to weakening and 2) the approaching negatively tilted upper-level trough, favoring intensification. Numerical hindcast simulations using the limited-area Mesoscale Compressible Community model with synthetic vortex insertion (cyclone bogus) prior to the ET of Hurricane Michael led to a more realistic evolution of wind and pressure compared to running the model without vortex insertion. Specifically, the mesoscale model correctly simulates the hurricane as the dominant circulation center early in the transition process, versus the baroclinic low to its north, which was the favored development in the runs not employing vortex insertion. A suite of experiments is conducted to establish the sensitivity of the ET to various initial conditions, lateral driving fields, domain sizes, and model parameters. The resulting storm tracks and intensities fall within the range of the operational guidance, lending support to the possibility of improving numerical forecasts using synthetic vortex insertion prior to ET in such a model
Prevalence of dysphagia in people with intellectual disability: a systematic review
Dysphagia (feeding and swallowing disorder) is associated with serious health complications and psychosocial sequelae. This review summarises international research relating to the prevalence of dysphagia in people with intellectual disability. Studies published from 1990 to July 2016 were identified using Medline, Cinahl, PsycINFO, Web of Science, email requests, and cross-citations. Twenty studies were identified. Dysphagia in people with intellectual disability appears to be associated with more severe intellectual disability, comorbid cerebral palsy, and motor impairments. However, further research with representative samples of people with intellectual disability using adequate methods of assessment are required in order to provide more precise prevalence estimates and clarify factors that may be associated with dysphagia in this population
- …